Octopamine, a biogenic amine, plays a major role as a transmitter, hormone, and neuromodulator in invertebrates (see P. D. Evans, Adv. Insect Physiol. 15:317-473 (1980), for review). Through the use of pharmacological and biochemical assays, specific receptors for octopamine have been identified in many invertebrate phyla, including arthropods and molluscs (J. A. Nathanson and P. Greengard, Science. 180:308-310 (1973); J. Axelrod and J. M. Saavedra, Nature 265:501-504 (1977); A. J. Harmer and A. S. Horn, Mol. Pharmacol. 13:512-520 (1977); R. J. Walker and G. A. Kerkut, Comp. Biochem. 61C:261-266 (1978); S. Konishi and E. A. Kravits, J. Physiol. 279:215-229 (1978); B. Battelle and E. A. Kravits, J. Pharmacol. Exp. Ther. 205:438-448 (1978); J. A. Nathanson, Science. 203: 65-68 (1979); R. P. Bodnaryk, Insect Biochem. 9: 155-162 (1979); B. Battelle et al., Experientia 35:778 (1979); E. A. Kravits et al. , J. Expo Biol. 89:159-175 (1980); P. D. Evans, J. Physiol. 318:99-122 (1981) and P. D. Evans, J. Exp. Bio. 129:239-250 (1987); M. S. Livingston et al., J. Neurobiol. 12: 27-54 (1981); A. Uzzan and Y. Dudai, J. Neurochem. 38:1542-1550 (1982); R. M. Harris-Warrick and E. A. Kravitz, J. Neurosci. 4: 1976-1993 (1984); P. D. Evans et al., J. Pharm. Pharmacol. 40:855-861 (1988)). Pharmacological studies in insects have provided evidence for the existence of multiple subtypes of octopamine receptors (P. D. Evans, Insect. Physiol. 15:317-473 (1980) , P. D. Evans, J. Physiol. 318:99-122 (1981), P. D. Evans, J. Exp. Biol. 129:239-250 (1987); P. D. Evans et al., J. Pharm. Pharmacol. 40:855-861 (1988)). In addition, there are reports indicating that octopamine receptors, pharmacologically distinct from adrenergic and dopamine receptors, exist in the mammalian central nervous system (T. P. Hicks and H. McLennan, Brain Res. 157:402-406 (1978), T. P. Hicks and H. McLennan, Br. J. Pharmacol. 64:485-491 (1978b); W. P. C. Dao and R. J. Walker, Experientia 36: 584-585 (1980)) .
Since octopamine receptors are selectively blocked by .alpha.-adrenergic antagonists and activated by .alpha.-adrenergic agonists, there has been speculation that octopamine receptors are closely related to vertebrate adrenergic receptors (P. D. Evans, Adv. Insect Physiol. 15:317-473 (1980), P. D. Evans, J. Physiol. 318:99-122 (1981), P. D. Evans, J. Exp. Biol. 129:239-250 (1987); J. C. Venter et al., Biochem. Pharmacol. 38:1197-1208 (1988)). However, there have been no structural data available to evaluate this hypothesis. Studies of octopamine receptors have also been complicated by the lack of specificity of available ligands both among the octopamine receptor subtypes and between octopamine receptors and receptors for other biogenic amines.
The present inventions are products, processes and compositions that relate, at least in part, to an octopamine receptor cDNA and to the protein product encoded therein. Sequence analysis of the cDNA reveals that the octopamine receptor is a member of the adrenergic/muscarinic/opsin gene superfamily of receptors (J. C. Venter et al., Prog. Neurobiol. 30:105-169 (1988; J. C. Venter et al., Biochem. Pharmacol. 38:1197-1208 (1989)). Permanent expression of this cDNA in mammalian cells provides the opportunity to study an octopamine receptor in isolation and thus, allows for the unambiguous description of a single receptor type. It also allows for a rapid and effective assay for the rational design in testing of insecticides targeted against the receptor.